feat(combat): add serializable Observation snapshot and LLMPolicy adapter

src/pf1e_simulator/combat.py

@@ -344,6 +344,41 @@ class ChargeResult:
     reason: str | None
 
 
+@dataclass(frozen=True)
+class Observation:
+    """Serializable snapshot of combat state for a policy/LLM.
+
+    Built by the engine at the point of policy invocation; the snapshot is the
+    ONLY source of information for an ``LLMPolicy`` — it never exposes
+    ``engine.*`` callables nor mutable references to live state. All collections
+    are copied (tuples/dicts) so the snapshot is frozen and JSON-serializable.
+
+    ``combatants`` holds one dict per combatant in ``self._states`` order;
+    ``pairs`` holds one dict per (acting combatant x each other combatant) with
+    ``target_index`` disambiguating the target. ``terrain`` and ``elevation``
+    are height x width layers aligned on the same dimensions (``elevation`` is
+    ``()`` when the grid has no elevation layer).
+    """
+
+    round: int
+    acting_combatant: int
+    combatants: tuple[dict[str, object], ...]
+    pairs: tuple[dict[str, object], ...]
+    terrain: tuple[tuple[str | None, ...], ...]
+    elevation: tuple[tuple[int, ...], ...]
+
+    def to_dict(self) -> dict[str, object]:
+        """Return a JSON-serializable dict with the pinned top-level keys."""
+        return {
+            "round": self.round,
+            "acting_combatant": self.acting_combatant,
+            "combatants": self.combatants,
+            "pairs": self.pairs,
+            "terrain": self.terrain,
+            "elevation": self.elevation,
+        }
+
+
 @dataclass(frozen=True)
 class SaveResult:
     """Outcome of one saving throw roll."""
@@ -446,14 +481,21 @@ class CombatEngine:
         *,
         round_cap: int = 100,
         policy: Policy | None = None,
+        llm_policy: LLMPolicy | None = None,
         spell_registry: dict[str, SpellSpec] | None = None,
         reaction_policy: ReactionPolicy | None = None,
     ) -> None:
+        if policy is not None and llm_policy is not None:
+            msg = "policy and llm_policy are mutually exclusive"
+            raise ValueError(msg)
         self._rng = rng
         self._grid = grid
         self._states = states
         self._round_cap = round_cap
-        self._policy = policy if policy is not None else default_policy
+        if llm_policy is not None:
+            self._policy = self._llm_adapter(llm_policy)
+        else:
+            self._policy = policy if policy is not None else default_policy
         self._spell_registry = spell_registry or {}
         self._reaction_policy = reaction_policy
         self._in_reaction = False
@@ -479,6 +521,108 @@ class CombatEngine:
         """The spell registry used for spell lookups."""
         return self._spell_registry
 
+    def _llm_adapter(self, llm_policy: LLMPolicy) -> Policy:
+        """Wrap an ``LLMPolicy`` into a ``Policy``.
+
+        At the point of invocation (``actions = self._policy(self, state)`` in
+        ``_take_turn``), the Observation is built for the current state and
+        delegated to ``llm_policy(observation, state)``. The adapter consumes
+        no RNG and mutates no state.
+        """
+
+        def adapter(_engine: CombatEngine, state: CombatantState) -> tuple[Action, ...]:
+            observation = self._build_observation(state)
+            return llm_policy(observation, state)
+
+        return adapter
+
+    def _build_observation(self, state: CombatantState) -> Observation:
+        """Build a frozen, serializable snapshot of the current combat state.
+
+        Pure read: never mutates state nor consumes RNG. ``state`` is the
+        acting combatant (the one whose turn it is).
+        """
+        acting_index = self._states.index(state)
+        combatants = tuple(self._combatant_snapshot(s) for s in self._states)
+        pairs = tuple(
+            self._pair_snapshot(state, target)
+            for target in self._states
+            if target is not state
+        )
+        terrain = tuple(
+            tuple(self._grid.terrain_at((r, c)).type for c in range(self._grid.width))
+            for r in range(self._grid.height)
+        )
+        has_elevation = getattr(self._grid, "_elevation", None) is not None
+        if has_elevation:
+            elevation = tuple(
+                tuple(
+                    self._grid.elevation_at((r, c)) for c in range(self._grid.width)
+                )
+                for r in range(self._grid.height)
+            )
+        else:
+            elevation = ()
+        return Observation(
+            round=self._current_round,
+            acting_combatant=acting_index,
+            combatants=combatants,
+            pairs=pairs,
+            terrain=terrain,
+            elevation=elevation,
+        )
+
+    def _combatant_snapshot(self, state: CombatantState) -> dict[str, object]:
+        """One per-combatant dict for the Observation (frozen copies)."""
+        conditions = tuple(
+            (c.condition.name, c.rounds_left) for c in state.active_conditions
+        ) + tuple((c.name, 0) for c in state.conditions)
+        resources = dict(state.resources_left)
+        for level, count in state.spell_slots_left.items():
+            resources[f"spell_slot_{level}"] = count
+        return {
+            "id": state.combatant.id,
+            "side": state.side,
+            "pos": state.pos,
+            "occupied_cells": tuple(sorted(state.occupied_cells())),
+            "hp": state.hp,
+            "hp_max": state.combatant.hp_max,
+            "active": state.active,
+            "dead": state.dead,
+            "conditions": conditions,
+            "resources_left": resources,
+            "weapon_broken": tuple(sorted(state.weapon_broken)),
+            "weapon_stolen": tuple(sorted(state.weapon_stolen)),
+            "grappled_with": state.grappled_with,
+            "moved_this_turn": state.moved_this_turn,
+            "power_attack": state.power_attack,
+        }
+
+    def _pair_snapshot(
+        self, state: CombatantState, target: CombatantState
+    ) -> dict[str, object]:
+        """One per-pair dict (acting combatant x target) for the Observation."""
+        distance_ft = self.creature_distance(state, target) * _SQUARE_FT
+        weapon = self.weapon_for(state, target)
+        weapon_name = weapon.name if weapon is not None else None
+        range_penalty = (
+            self.range_penalty(weapon, distance_ft) if weapon is not None else 0
+        )
+        charge = self.can_charge(state, target)
+        can_charge = charge is not None and charge.weapon is not None
+        return {
+            "target_index": self._states.index(target),
+            "distance_ft": distance_ft,
+            "weapon_for": weapon_name,
+            "range_penalty": range_penalty,
+            "can_charge": can_charge,
+            "can_step5_to_attack": self.can_step5_to_attack(state, target),
+            "has_line_of_effect": has_line_of_effect_cells(
+                self._grid, state.occupied_cells(), target.occupied_cells()
+            ),
+            "flanking": self._flanking_bonus(state, target) > 0,
+        }
+
     def _take_turn(self, state: CombatantState) -> bool:
         """Execute one combatant's full turn; return True if the battle is over."""
         self._decrement_durations(state)
@@ -3289,6 +3433,8 @@ def _nauseated_filter(actions: tuple[Action, ...]) -> tuple[Action, ...]:
 
 Policy = Callable[[CombatEngine, CombatantState], tuple[Action, ...]]
 
+LLMPolicy = Callable[[Observation, CombatantState], tuple[Action, ...]]
+
 ReactionPolicy = Callable[
     [CombatEngine, CombatantState, ReactionEvent], Action | None
 ]

tests/test_observation.py

@@ -0,0 +1,497 @@
+"""Tests for L1: serializable Observation snapshot + LLMPolicy adapter.
+
+Covers the pinned schema:
+- Per-combatant fields (id, side, pos, occupied_cells, hp/hp_max, active/dead,
+  conditions, resources_left + spell_slot_* keys, weapon_broken/weapon_stolen,
+  grappled_with, moved_this_turn, power_attack).
+- Per-pair fields (target_index, distance_ft, weapon_for, range_penalty,
+  can_charge, can_step5_to_attack, has_line_of_effect, flanking).
+- Terrain/elevation layers.
+- Frozen copies: mutating live state after construction does not change the
+  already-built Observation.
+- ``to_dict()`` is JSON-serializable and exposes no ``engine.*`` callables.
+- The ``llm_policy`` adapter builds the Observation at the point of policy
+  invocation and delegates to ``llm_policy(observation, state)``.
+"""
+
+from __future__ import annotations
+
+import json
+
+import pytest
+
+from pf1e_simulator.combat import Action, CombatantState, CombatEngine, Observation
+from pf1e_simulator.conditions import SHAKEN
+from pf1e_simulator.dice import parse_dice
+from pf1e_simulator.effects import ActiveCondition
+from pf1e_simulator.grid import Grid
+from pf1e_simulator.map import MapSpec, TerrainType
+from pf1e_simulator.models import (
+    AbilityScores,
+    ACProfile,
+    AttackSpec,
+    Combatant,
+    DamageComponent,
+    Saves,
+)
+from pf1e_simulator.rng import ScriptedRng
+
+
+def make_combatant(
+    cid: str,
+    *,
+    size: str = "Medium",
+    hp: int = 20,
+    ac: int = 15,
+    attack_bonus: int = 5,
+    speed: int = 30,
+    ranged: bool = False,
+) -> Combatant:
+    """Build a single-weapon combatant (melee by default, ranged if requested)."""
+    if ranged:
+        attack = AttackSpec(
+            id=f"{cid}-w",
+            name="short bow",
+            kind="ranged",
+            attack_bonus=attack_bonus,
+            damage=[DamageComponent(formula=parse_dice("1d6"), types=["piercing"])],
+            range_increment_ft=60,
+        )
+    else:
+        attack = AttackSpec(
+            id=f"{cid}-w",
+            name="short sword",
+            kind="melee",
+            attack_bonus=attack_bonus,
+            damage=[DamageComponent(formula=parse_dice("1d6"), types=["slashing"])],
+        )
+    return Combatant(
+        id=cid,
+        name=cid,
+        level=1,
+        size=size,
+        abilities=AbilityScores(
+            str_score=10,
+            dex_score=10,
+            con_score=12,
+            int_score=10,
+            wis_score=10,
+            cha_score=10,
+        ),
+        hp_max=hp,
+        ac=ACProfile(total=ac, touch=ac, flat_footed=ac),
+        bab=attack_bonus,
+        initiative_mod=0,
+        speed_land_ft=speed,
+        saves=Saves(fort=0, ref=0, will=0),
+        attacks=[attack],
+    )
+
+
+def make_state(combatant: Combatant, side: str, pos: tuple[int, int]) -> CombatantState:
+    return CombatantState(combatant=combatant, side=side, pos=pos, hp=combatant.hp_max)
+
+
+def make_grid(*, elevation: bool = False) -> Grid:
+    legend = {".": TerrainType(type="floor", move_cost=1)}
+    spec = MapSpec(
+        name="test",
+        terrain=tuple(["." * 8] * 8),
+        legend=legend,
+        elevation=tuple(["0" * 8] * 8) if elevation else None,
+    )
+    return Grid.from_spec(spec)
+
+
+def make_engine(states: list[CombatantState], *, grid: Grid | None = None) -> CombatEngine:
+    return CombatEngine(ScriptedRng([]), grid or make_grid(), states)
+
+
+def _snapshot(engine: CombatEngine, state: CombatantState) -> dict:
+    return engine._build_observation(state).to_dict()
+
+
+# ---------------------------------------------------------------------------
+# 1. Basic 1v1 schema — all combatant fields present and correct
+# ---------------------------------------------------------------------------
+
+
+def test_observation_basic_schema_1v1() -> None:
+    """Given: a simple 1v1 with default state
+    When: an Observation is built for the acting combatant
+    Then: every per-combatant field is present and correct."""
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    foe_state = make_state(foe, "monsters", (0, 3))
+    engine = make_engine([hero_state, foe_state])
+
+    obs = _snapshot(engine, hero_state)
+
+    assert obs["round"] == 0
+    assert obs["acting_combatant"] == 0
+    assert len(obs["combatants"]) == 2
+
+    c = obs["combatants"][0]
+    assert c["id"] == "hero"
+    assert c["side"] == "players"
+    assert c["pos"] == (0, 0)
+    assert c["occupied_cells"] == ((0, 0),)
+    assert c["hp"] == 20
+    assert c["hp_max"] == 20
+    assert c["active"] is True
+    assert c["dead"] is False
+    assert c["conditions"] == ()
+    assert c["resources_left"] == {}
+    assert c["weapon_broken"] == ()
+    assert c["weapon_stolen"] == ()
+    assert c["grappled_with"] is None
+    assert c["moved_this_turn"] is False
+    assert c["power_attack"] is False
+
+
+# ---------------------------------------------------------------------------
+# 2. Conditions → (name, rounds_left) tuples
+# ---------------------------------------------------------------------------
+
+
+def test_observation_conditions() -> None:
+    """Given: a combatant with an active condition (shaken 2 rounds)
+    When: an Observation is built
+    Then: conditions contains (name, rounds_left)."""
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    hero_state.active_conditions.append(
+        ActiveCondition(condition=SHAKEN, rounds_left=2, source="test")
+    )
+    foe_state = make_state(foe, "monsters", (0, 3))
+    engine = make_engine([hero_state, foe_state])
+
+    c = _snapshot(engine, hero_state)["combatants"][0]
+    assert c["conditions"] == (("shaken", 2),)
+
+
+# ---------------------------------------------------------------------------
+# 3. weapon_broken / weapon_stolen listed
+# ---------------------------------------------------------------------------
+
+
+def test_observation_weapon_broken_stolen() -> None:
+    """Given: a combatant with a broken and a stolen weapon
+    When: an Observation is built
+    Then: weapon_broken and weapon_stolen list the ids (sorted)."""
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    hero_state.weapon_broken = {"hero-w"}
+    hero_state.weapon_stolen = {"hero-w"}
+    foe_state = make_state(foe, "monsters", (0, 3))
+    engine = make_engine([hero_state, foe_state])
+
+    c = _snapshot(engine, hero_state)["combatants"][0]
+    assert c["weapon_broken"] == ("hero-w",)
+    assert c["weapon_stolen"] == ("hero-w",)
+
+
+# ---------------------------------------------------------------------------
+# 4. grappled_with / moved_this_turn / power_attack reflected
+# ---------------------------------------------------------------------------
+
+
+def test_observation_grappled_moved_power_attack() -> None:
+    """Given: a combatant that is grappled, has moved, and uses power attack
+    When: an Observation is built
+    Then: the three flags are reflected."""
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    hero_state.grappled_with = "foe"
+    hero_state.moved_this_turn = True
+    hero_state.power_attack = True
+    foe_state = make_state(foe, "monsters", (0, 3))
+    engine = make_engine([hero_state, foe_state])
+
+    c = _snapshot(engine, hero_state)["combatants"][0]
+    assert c["grappled_with"] == "foe"
+    assert c["moved_this_turn"] is True
+    assert c["power_attack"] is True
+
+
+# ---------------------------------------------------------------------------
+# 5. Pairs: distance_ft, weapon_for, range_penalty
+# ---------------------------------------------------------------------------
+
+
+def test_observation_pairs_distance_weapon_range_penalty() -> None:
+    """Given: a melee attacker adjacent to a target and a ranged attacker at
+    the second range increment
+    When: an Observation is built
+    Then: distance_ft is 5 for adjacent, weapon_for is the weapon name,
+    range_penalty is -2 for a ranged weapon at the second increment."""
+    # Adjacent melee pair
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    foe_state = make_state(foe, "monsters", (0, 1))
+    engine = make_engine([hero_state, foe_state])
+
+    pairs = _snapshot(engine, hero_state)["pairs"]
+    assert len(pairs) == 1
+    p = pairs[0]
+    assert p["target_index"] == 1
+    assert p["distance_ft"] == 5
+    assert p["weapon_for"] == "short sword"
+    assert p["range_penalty"] == 0
+
+    # Ranged attacker at 15 cells (75 ft) with 60 ft increment → second increment
+    archer = make_combatant("archer", ranged=True)
+    target = make_combatant("target")
+    archer_state = make_state(archer, "players", (0, 0))
+    target_state = make_state(target, "monsters", (0, 15))
+    engine2 = make_engine([archer_state, target_state])
+
+    p2 = _snapshot(engine2, archer_state)["pairs"][0]
+    assert p2["distance_ft"] == 75
+    assert p2["weapon_for"] == "short bow"
+    assert p2["range_penalty"] == -2
+
+
+# ---------------------------------------------------------------------------
+# 6. Pairs: can_charge and has_line_of_effect
+# ---------------------------------------------------------------------------
+
+
+def test_observation_pairs_can_charge_and_los() -> None:
+    """Given: a clear straight line vs a wall blocking LoS
+    When: an Observation is built
+    Then: can_charge is True on the clear line, False behind the wall, and
+    has_line_of_effect is False behind blocks_los."""
+    # Clear straight line: 3 cells apart, no obstacles
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    foe_state = make_state(foe, "monsters", (0, 3))
+    engine = make_engine([hero_state, foe_state])
+    p = _snapshot(engine, hero_state)["pairs"][0]
+    assert p["can_charge"] is True
+    assert p["has_line_of_effect"] is True
+
+    # Wall between them blocks LoS and charge
+    legend = {
+        ".": TerrainType(type="floor", move_cost=1),
+        "#": TerrainType(type="wall", move_cost=None, blocks_los=True),
+    }
+    walled = MapSpec(
+        name="test",
+        terrain=(
+            "........",
+            "........",
+            "..####..",
+            "..#..#..",
+            "..#..#..",
+            "..####..",
+            "........",
+            "........",
+        ),
+        legend=legend,
+    )
+    grid = Grid.from_spec(walled)
+    hero2 = make_combatant("hero2")
+    foe2 = make_combatant("foe2")
+    hero2_state = make_state(hero2, "players", (0, 0))
+    foe2_state = make_state(foe2, "monsters", (3, 3))
+    engine2 = CombatEngine(ScriptedRng([]), grid, [hero2_state, foe2_state])
+    p2 = _snapshot(engine2, hero2_state)["pairs"][0]
+    assert p2["can_charge"] is False
+    assert p2["has_line_of_effect"] is False
+
+
+# ---------------------------------------------------------------------------
+# 7. Pairs: flanking
+# ---------------------------------------------------------------------------
+
+
+def test_observation_pairs_flanking() -> None:
+    """Given: an ally on the opposite side of the target
+    When: an Observation is built
+    Then: flanking is True for the melee attacker."""
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    ally = make_combatant("ally")
+    hero_state = make_state(hero, "players", (3, 3))
+    foe_state = make_state(foe, "monsters", (3, 4))
+    ally_state = make_state(ally, "players", (3, 5))
+    engine = make_engine([hero_state, foe_state, ally_state])
+
+    p = _snapshot(engine, hero_state)["pairs"][0]
+    assert p["target_index"] == 1
+    assert p["flanking"] is True
+
+
+# ---------------------------------------------------------------------------
+# 8. Terrain / elevation layers
+# ---------------------------------------------------------------------------
+
+
+def test_observation_terrain_elevation() -> None:
+    """Given: a map with and without an elevation layer
+    When: an Observation is built
+    Then: terrain is filled with type names; elevation has values when present
+    and () when absent."""
+    # With elevation
+    legend = {".": TerrainType(type="floor", move_cost=1)}
+    spec = MapSpec(
+        name="test",
+        terrain=("..", ".."),
+        legend=legend,
+        elevation=("01", "00"),
+    )
+    grid = Grid.from_spec(spec)
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    foe_state = make_state(foe, "monsters", (1, 1))
+    engine = CombatEngine(ScriptedRng([]), grid, [hero_state, foe_state])
+
+    obs = _snapshot(engine, hero_state)
+    assert obs["terrain"] == (("floor", "floor"), ("floor", "floor"))
+    assert obs["elevation"] == ((0, 1), (0, 0))
+
+    # Without elevation
+    hero2 = make_combatant("hero2")
+    foe2 = make_combatant("foe2")
+    hero2_state = make_state(hero2, "players", (0, 0))
+    foe2_state = make_state(foe2, "monsters", (1, 1))
+    engine2 = make_engine([hero2_state, foe2_state])
+    obs2 = _snapshot(engine2, hero2_state)
+    assert obs2["terrain"] == (("floor",) * 8,) * 8
+    assert obs2["elevation"] == ()
+
+
+# ---------------------------------------------------------------------------
+# 9. to_dict() is JSON-serializable and exposes no engine.* callables
+# ---------------------------------------------------------------------------
+
+
+def test_observation_to_dict_json_serializable_no_engine_ref() -> None:
+    """Given: a built Observation
+    When: to_dict() is called
+    Then: json.dumps succeeds and the dict contains only builtins (no
+    engine.* callables, no mutable shared references)."""
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    foe_state = make_state(foe, "monsters", (0, 3))
+    engine = make_engine([hero_state, foe_state])
+
+    obs = engine._build_observation(hero_state)
+    data = obs.to_dict()
+    json.dumps(data)  # must not raise
+
+    # No callable values anywhere in the serialized dict
+    def assert_no_callables(value: object) -> None:
+        assert not callable(value), f"callable exposed in snapshot: {value!r}"
+        if isinstance(value, dict):
+            for v in value.values():
+                assert_no_callables(v)
+        elif isinstance(value, (list, tuple)):
+            for v in value:
+                assert_no_callables(v)
+
+    assert_no_callables(data)
+
+
+# ---------------------------------------------------------------------------
+# 10. Frozen copies: mutating live state after construction
+# ---------------------------------------------------------------------------
+
+
+def test_observation_frozen_copies() -> None:
+    """Given: an Observation already built
+    When: the live state's weapon_broken, resources_left, and the grid change
+    Then: the already-built Observation does not change."""
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    foe_state = make_state(foe, "monsters", (0, 3))
+    engine = make_engine([hero_state, foe_state])
+
+    obs = engine._build_observation(hero_state)
+    data_before = obs.to_dict()
+
+    # Mutate live state after construction
+    hero_state.weapon_broken.add("hero-w")
+    hero_state.resources_left["rage"] = 3
+    hero_state.spell_slots_left[1] = 2
+    hero_state.hp = 5
+    hero_state.pos = (5, 5)
+
+    data_after = obs.to_dict()
+    assert data_after == data_before
+    assert data_after["combatants"][0]["hp"] == 20
+    assert data_after["combatants"][0]["pos"] == (0, 0)
+    assert data_after["combatants"][0]["weapon_broken"] == ()
+    assert data_after["combatants"][0]["resources_left"] == {}
+
+
+# ---------------------------------------------------------------------------
+# 11. LLMPolicy adapter e2e
+# ---------------------------------------------------------------------------
+
+
+def test_llm_policy_wrapper_e2e() -> None:
+    """Given: a CombatEngine with an llm_policy that reads ONLY the observation
+    When: the battle runs
+    Then: the policy's decisions are honored and the transcript is coherent."""
+
+    def llm_policy(obs: Observation, state: CombatantState) -> tuple:
+        # Read only the observation: full_attack if the target is adjacent,
+        # otherwise move toward it.
+        target_id = obs.combatants[obs.pairs[0]["target_index"]]["id"]
+        if obs.pairs and obs.pairs[0]["distance_ft"] <= 5:
+            return (Action(kind="full_attack", target_id=target_id),)
+        return (Action(kind="move", target_id=target_id),)
+
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    foe_state = make_state(foe, "monsters", (0, 3))
+    engine = CombatEngine(
+        ScriptedRng([10, 9, 8, 15, 3, 5]),
+        make_grid(),
+        [hero_state, foe_state],
+        round_cap=1,
+        llm_policy=llm_policy,
+    )
+
+    result = engine.run()
+    # The hero is 3 cells away → moves first, then attacks on a later turn.
+    assert any("move" in line for line in result.transcript)
+
+
+# ---------------------------------------------------------------------------
+# 12. policy + llm_policy → ValueError
+# ---------------------------------------------------------------------------
+
+
+def test_llm_policy_and_policy_value_error() -> None:
+    """Given: both policy and llm_policy provided
+    When: the engine is constructed
+    Then: ValueError is raised."""
+    hero = make_combatant("hero")
+    foe = make_combatant("foe")
+    hero_state = make_state(hero, "players", (0, 0))
+    foe_state = make_state(foe, "monsters", (0, 3))
+
+    def llm_policy(obs: Observation, state: CombatantState) -> tuple:
+        return ()
+
+    with pytest.raises(ValueError, match="mutually exclusive"):
+        CombatEngine(
+            ScriptedRng([]),
+            make_grid(),
+            [hero_state, foe_state],
+            policy=lambda _e, _s: (),
+            llm_policy=llm_policy,
+        )